The invention relates, generally, to disc drive systems and methods of making, testing and using the same, which involve arranging a plurality of heads and recording surfaces in a stack and in preferred embodiments to such systems and methods wherein data is associated with the plurality of heads depending on a head location scheme for maximizing manufacturing flexibility. Further embodiments involve defining a reading or recording scheme in which data is read or recorded, using an array of heads operated in seriatim and an alternating order relative to the stack of recording surfaces.
Modern computers employ various forms of storage systems for storing programs and data. For example, various forms of disc drive systems have been designed to operate under the control of a computer to record information and/or retrieve recorded information on one or more recording discs. Such disc drives include hard disc drives which employ recording discs that have magnetizable (hard) recording material, optical disc drives which employ recording discs that have optically readable recording material, magneto-optical (MO) disc drives which employ recording discs that have optically readable magnetizable recording material, or the like.
Conventional disc drive systems typically include one or more recording discs supported for relatively high speed rotation on a rotary spindle. In systems employing more than one recording disc, the discs are typically arranged in a stack on the spindle. The recording surfaces of such stacked discs are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which form a part of an actuator assembly. Typically, the actuator assembly has an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. A motor selectively positions a proximal end of the actuator body. This positioning of the proximal end in cooperation with the pivot mechanism causes a distal end of the actuator body, which supports the read/write heads, to move generally radially across the recording surfaces of the discs, such that the head may be selectively positioned adjacent any recording location on the recording surface, as the disc is rotated.
In operation, the heads are moved in the generally radial direction to align or register with a desired track locations on the recording surfaces of the discs. Once aligned or registered with the desired track location, the heads are operated to read or write information onto the recording surface at the desired track location.
For example, FIG. 1 shows a top-down view of a single disc recording surface 11 of disc 10, which may, for example, be the top disc in a stack of discs. FIG. 1 also shows a head assembly structure, supporting a recording and/or reading head 12 adjacent the recording surface 11. The recording surface 11 defines multiple, concentric recording tracks. While modern recording disc technology allows for a much greater track density than that shown in FIG. 1, a number of widely spaced tracks, labeled 0-4 are illustrated in exaggerated widths and interspacings, to simplify the drawings.
In FIG. 1, the head 12 is supported on a suspension member 13 of a head support arm 14. As described above, the arm 14 is coupled to (or part of) an actuator, such as a voice coil motor or other suitable actuation device 16. Also as described above, the actuator 16 is connected to suitable control electronics for controlled movement of the arm 14 and, thus, controlled positioning of the head 12 relative to the radial dimension of the disc surface 11.
More specifically, selective activation of the actuator 16 causes selective pivotal movement of arm 14 about the pivot joint 15. Such selective pivotal arm motion results in selective motion of the head 12 in the cross-track direction (generally in the radial dimension of the disc surface), as indicated by arrows 18. In this manner, the head 12 may be selectively positioned adjacent a particular track for recording and/or reading on that track. For example, in FIG. 1, the head 12 is positioned for reading and/or recording on track 3. However, by selectively activating the actuator 16 to pivot the arm 14, the head 12 may be moved to a new head position, adjacent another track.
During reading or recording operations, the disc is rotated on a spindle hub 20. The disc rotation is represented in FIG. 1 by arrow 19. For any given head position (such as the track 3 position of head 12 in FIG. 1), the entire track passes adjacent the head in each compete revolution of the disc. Moreover, as described above, the head 12 may be selectively moved to any track location on the disc. Thus, the head 12 may be capable of being positioned, relative to the disc surface 11, for reading or recording data on any portion of any track on the disc surface. For further recording capacity, double-sided disc systems employ a second head 22 similarly supported and positionable adjacent a second set of recording tracks on the opposite facing surface 21 of disc 10, as shown in FIG. 2.
Yet greater recording capacity and recording or retrieving speeds can be achieved with multiple disc systems. As can be readily appreciated, for a given disc size and recording density, the recording capacity of a multiple disc system can increase by up to about N times the capacity of a single disc system, wherein N is the number of discs in the multiple disc system. In addition, multiple disc systems can provide improved recording and/or reading speeds, relative to single disc systems, in that data may be read from multiple tracks (one track for each disc surface) at each given track position of the head array. In contrast, for a single disc system, at most, two tracks may be read or recorded (in a double-sided disc arrangement) before the head array must seek the next track position, resulting in greater overall head re-positioning delays, as compared to the capabilities of multiple disc system technology.
The number of discs included in a disc drive system is typically based on the demands of the intended application of use of the system. Various factors, such as, but not limited to recording capacity, speed, cost, size, weight and the like can affect the determination of the number of discs (and heads) to be included in a particular disc drive system. As a whole, the demand in the disc drive industry varies widely. Some applications of use require the capability to store large amounts of data or fast retrieval and/or recording speeds and, thus, require a relatively large number of discs. Yet other applications require low cost and/or involve lower storage capacity demands and, thus, require fewer discs. However, it is typically not economically efficient to design a completely different disc drive system for each different application of use.
Accordingly, there is a need in the disc drive industry to meet such varying demands and, at the same time, produce high quality products in a cost efficient manner.
Furthermore, in many applications of use of disc drive systems having a stack arrangement of discs and heads, it is desirable to maximize the reading or recording speed. In typical multiple disc systems, a plurality of discs are arranged in a stack on a common hub, such that track 1 of each disc in the stack is generally in alignment with track 1 of the other discs in the stack, track 2 of each disc is generally aligned with track 2 of the other discs, and so forth. In this manner the generally aligned tracks of the stack of discs define concentric cylinders, which correspond to the similarly numbered tracks in FIG. 1, as cylinder 0, cylinder 1, cylinder 2, and so forth. A plurality of heads on a common head/arm actuator structure are arranged in an array adjacent the discs in the stack such that a respective head is associated with each respective recording surface in the disc stack.
As the array is moved by the actuator in the cross-track direction (for example, the general radial direction of the disc), the heads in the array become aligned with tracks on the disc recoding surfaces in the stack and, when properly aligned, may be operated to access such tracks, for example as part of a record or read operation. If the heads are arranged in the array to substantially simultaneously seek tracks in a common cylinder with respect to the other heads in the array, then at each cylinder position of the head array along the cross-track (or generally radial) movement, a plurality of tracks (or all of the tracks) in a common cylinder may accessed by switching the reading or recording operation from one head to another (typically, with minor alignment adjustments upon switching operation between heads).
More particularly, if simultaneous alignment were achieved, then at each given cylinder position of the head array, a reading or recording operation requiring a plurality of tracks could be carried out over a plurality of discs, by operating a plurality of heads in series without seeking a further track (cylinder) position. While there is typically some delay associated with electronically switching the reading or recording operation from one head to another, it is typically faster to electronically switch heads and make minor alignment adjustments (to effectively switch from one track to another), as compared to physically moving a head from one track location to seek another track location and then re-aligning the head at the new track position on a single disc surface.
Accordingly, for recording or reading operations involving more than one track, disc drive systems having multiple heads and multiple recording surfaces (including those involving multiple discs) arranged in a stack can be operated to switch the recording or reading operation from one head to another head to change tracks during recording or reading to improve recording or reading speed. However, even with such head switching functions, where a reading or recording operation involves more tracks than the number of heads in the array, the actuator still must be controlled to seek a further track (or cylinder) position during the recording or reading operation, to reposition the heads adjacent additional tracks, for example, of the next cylinder. Such track seeking operations result in further delays.
The overall reading or recording speed may, therefore, depend, in part, on the delays associated with switching heads and with seeking track (or cylinder) positions of the head array. Accordingly, there is a further need in the industry for minimizing such delays and, therefore, maximizing the reading or recording speed capability of disc drive systems and processes.
Therefore, embodiments of the present invention involve disc drive systems and methods for making, using and testing the same, to address varying industry demands and provide manufacturing flexibility to meet the varying demands in a cost efficient manner.
Further embodiments of the present invention involve disc drive systems and methods for making and using the same for maximizing the reading or recording speed capability of disc drive systems and processes.
According to embodiments of the present invention disc drive systems and methods for making, testing and using the same involve arrangements of discs and heads and processes or means for defining the head locations and mapping data to correspond to such head locations in a manner which maximizes the flexibility of a system design to accommodate a variety of different disc totals. With such flexibility, the same general system design (with minimal modifications) may accommodate a variety of different disc drive systems, to meet a variety of different industry demands.
In preferred embodiments, disc and head locations are defined in a manner to cost efficiently accommodate at least two (and more preferably, three) different disc totals. For example, in one preferred embodiment, a disc drive system design can accommodate a total of either two, three or four discs, with minimal modifications to the disc drive device hardware and software. According to one aspect of the invention, the same hub may be employed with either the two, three or four disc system, wherein the selected number of discs are arranged on a spindle in a manner which most efficiently maintains balance and also accommodates easy removal or addition of discs during manufacture to define or re-define the total number of discs in the system. According to a further aspect of the invention, test and operation data and parameters that are normally associated with each head, based on the physical location of the head, are mapped to be associated with that two, three or four disc arrangement and, thus head assignments associated therewith. Principles of the invention may be applied to other systems involving combinations of different disc totals other than the two, three and four disc combination described above.
In further preferred embodiments, a reading or recording scheme involves operating an array of heads in seriatim and an alternating order relative to the stack of recording surfaces. For example, as the actuator moves the head array in the cross-track direction (for example, the general radial direction of the disc), the heads in the array become aligned with tracks on the disc recoding surfaces in the stack. Preferably the head array is arranged such that a plurality (and more preferably, all) of the heads in the array are at least generally aligned with a respective track at about the same time. By operating a plurality of heads in the array in at each alignment position, a plurality of tracks in mutually different levels of the stack may be accessed in series, as part of a reading or recording operation. Thus, while minor alignments may be needed as the reading or recording operation switches from one head to another, a track seeking operation need not be required when switching heads.
Once the head array operation has been switched one pass through the series of heads (for example, from the top of the stack, down, or from the bottom of the stack, up), a further track position may be sought and the head array continues its cross-track movement toward the next track position. However, instead of returning the head operation to the beginning of the series defined by the previous pass (at the previous track alignment position), the head operation continues with the operation of the head last operated in the previous pass. Operation thereafter switches through the array of heads, in series, but in reverse order with respect to the order of the previous pass (at the previous track alignment position).
As a result, a recording or reading operation involves switching operation of the heads in the array in series with respect to the stack (for example, top down or bottom up) at each general track alignment position in the cross-track (generally radial) motion of the head array, and alternating the direction in which the heads are operated at each new track alignment position of the head array, with respect to the previous track alignment position. In this regard, switching access from one track to another during a recording or reading operation involves either switching from one head to another in the series (and, possibly, minor alignment adjustments) or a track seek operation to seek the next track location at the end of a series pass. Unlike prior disc stack systems, however, switching access between tracks would not require both a head switching and a track seeking operation. That is, the head operated as the last head in the series at the previous pass (previous track position of the head array) is the same head that is operated as the first head in the series at the present pass (present track position).
Thus, switching from one track to another during a reading or recording operation involves either a delay associated with switching heads or a delay associated with seeking a next track, and need not involve both delays at any one track switching time. Substantial advantages with respect to minimizing track switching delays are, therefore, available when the head array is operated in series, but alternating order as described herein.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.